Technically, beavers are a mammal due to their milk producing abilities, fur/hair, and method of giving birth (live births as opposed to laying eggs). However, that didn’t stop the Roman Catholic Church from declaring beaver a fish during the 17th century.
For those of you who don’t have much experience with Catholicism, the 40 days before Easter are called Lent and during Lent you are not supposed to eat meat on Fridays, with the exception of fish. Now, the Bishop of Quebec was pondering whether or not he could eat beaver meat during Lent, and decided to follow Thomas Aquinas’ judgement in the Summa Theologica that an animal’s classification is determined by both habitat and anatomy. So, due to the aquatic nature of beavers habitat, the Bishop of Quebec figured that beavers ought to count as a fish since they live in ponds. Thus, people could eat beaver meat during Lent without worrying about breaking any rules.
Make no mistake, scientifically speak beavers are absolutely not a fish. And I don’t know about you, but I don’t think I’ll be chowing down on beaver meat anytime soon – regardless of whether the Catholic Church considers it a fish or mammal.